The invention relates generally to inflatable restraint systems for protecting an occupant of an automotive vehicle and the like from side impacts and, more particularly, to an improved inflatable restraint system that protects the head, thorax, and pelvis of an occupant from side impacts by restraining the movement of the occupant and cushioning contact between the occupant and structural members of the vehicle body during a collision.
An inflatable restraint system for protecting the head and torso regions of an occupant of an automotive vehicle from injury during side impacts is disclosed in U.S. Pat. No. 4,966,388 (hereinafter "the '388 patent"). The disclosure of this patent was developed by the assignee of the present invention and is incorporated by reference herein. In this patent, an air bas assembly mounted in a side door of a vehicle is designed to be fully deployed in about 30 to 50 milliseconds after a side impact of the vehicle is sensed. The air bag inflates from a stored position in a cavity in the side door to a deployed position forming a barrier for preventing injury to the occupant's head, neck, and shoulders.
In further developing such an inflatable restraint system, the assignee of the present invention identified several aspects of the prior system which could be improved. First of all was a recognition of the need to provide protection for the pelvic regions of the occupant and to better control the deployment of the bag to direct it toward the occupant.
As evident from FIG. 3 of the '388 patent, the fully deployed air bag only covers the head and shoulder regions of the occupant. Although inflation of the air bag propels a hinged door portion of a cushioning panel toward the occupant's torso, it is clear from FIG. 3 that only the top of the cushioning panel is propelled toward the occupant. Furthermore, the air bag itself does not afford any protection in the pelvic region.
Another area where there is always room for improvement in systems of this type is in the deployment of the air bag from its stowed position to its fully inflated position. As the lateral distance between the occupant and the side of the vehicle is generally small, the air bag must be deployed as quickly as possible, especially to allow the bag to expand upwardly to protect the head of the occupant. Thus, in the '388 patent it was noted that the timing of the deployment of the air bag is absolutely critical. For example, in a 28 mile per hour side impact, each millisecond delay represents about one-half inch of side panel or door penetration. Thus, the invention also is directed to enhancing deployment of the bag to ensure it is inflated quickly enough to provide adequate protection for the head, thoracic, and pelvic regions of the occupant.
In the prior restraint system, the stowed air bag directly contacts the inner surface of the foamed cushioning panel. (See, for example, FIGS. 1 and 3 of the '388 patent). The contact between the outer surface of the air bag, typically nylon material, and the foamed cushioning panel, typically polyethylene, produces frictional forces, which hinder rapid deployment of the air bag. This friction can retard the inflation of the air bag by restraining the immediate deployment of the bag.
The folding technique employed to store an air bag in its stowed position also affects its deployment. As illustrated in FIGS. 8-12 of the '388 patent, the prior folding technique involved folding protruding fore and aft sections of the bag inwardly so as to lie over or be nested inside the central, generally rectangular portion of the bag. The upper one-third portion of the rectangular configuration was then folded about the bottom edge of the central portion to overlie the front of the lower one-third portion of the bag. A final S-shaped fold in the free upper edge of the upper portion could then be made.
The resulting pouch was then inserted into a cavity in the side panel such that the upper portion of the bag faced the interior of the vehicle. As specifically noted in column 6, lines 23-30, of the '388 patent, this folding technique required the bag to expand laterally toward the interior of the vehicle before inflation in the vertical direction occurred. As a result, the bag tended to rotate around the upper folding line of the bag and the lower section of the bag would have to be almost completely inflated before the upper half of the bag would inflate. This resulted in the possibility of the bag not expanding upwardly quickly enough to protect the occupant's head.
Finally, the air bag of the '388 patent employed internal tethers to control the shape of the bag in its deployed condition and add to its strength. As illustrated in FIGS. 6, 7, 13, and 14 of the '388 patent, each tether was stitched between opposed sides of the bag in a position with its longitudinal dimension arranged along a radial line emanating from the inflator. As the thrust of the gas generated by the inflator emanates spherically therefrom, the stress on the tethers caused by the deployment of the air bag is greatest at the end of the tether closest to the inflator. Thus, depending upon the particular geometry of the bag, pressure of the inflator gas, etc., such a radial tether arrangement could lead to the tearing of the tethers or of the bag itself along the radial stitching where the tethers are attached.